● Genes are basic units of heredity
● Heredity is the way genes transmit traits
● Traits are often caused by interactions between many genes
● Artificial Selection: purposeful control over mating by choice of parents
● Self fertilizing: both egg and pollen come from the same plant
● Pure Breeding lines: produce offspring that carry parental traits that remain the same in
each generation (also called inbred)
○ Plants with white flowers always produced white flowers
○ Plants with purple flowers always produced purple flowers
● Crossed pure-breeding plants with alternative traits to to produce hybrids which
contained characteristics of one parent
● Mendel dusted female stigma of green pea flower plant with pollen from yellow pea
plants (familial generation) and vice versa
○ The peas were yellow in both cases because yellow is the dominant (first filial F1
generation)
○ Monohybrid Cross: involving hybrid for a single trait
■ Mendel planted the peas to obtain mature F1 plants that he self fertilized
and harvested (fertilized yellow pea plants with other pea plants) and
counted the peas of the resulting F2 generation
● 3:1 ratio of yellow to green peas (Yy x Yy)
○ ¼ breed true for dominant trait
○ ½ will be hybrids
○ ¼ will breed for the recessive trait
○ Pea plants are diploid and there are two alleles of a gene
● For each trait, every plant carries around two copies of a gene
○ Dominant: appeared in all F1 hybrids
■ All genes are not dominant, normally there are variations (not 100%)
■ Incomplete dominance:
■ Codominance:
○ Common misconceptions: Dominant alleles aren’t more prevalent or more “fit”
than recessive alleles and don’t dominate recessive alleles
○ Recessive: remained hidden in F1 hybrids but reappeared in F2 generation
● Each gene comes in alternative forms (alleles)
○ Ex: gene for seed color has yellow and green alleles
● Monohybrids: individuals having two different alleles for a single trait
● During the formation of eggs and sperm, two copies of gene in each parent separate so
each gamete only receives one allele for each trait
● Law of Segregation: two alleles for each trait separate during gamete formation and
unite at random, at fertilization, from each parent
○ Each gamete has ½ chance of carrying dominant allele and ½ chance of carrying
recessive
● Heredity is the way genes transmit traits
● Traits are often caused by interactions between many genes
● Artificial Selection: purposeful control over mating by choice of parents
● Self fertilizing: both egg and pollen come from the same plant
● Pure Breeding lines: produce offspring that carry parental traits that remain the same in
each generation (also called inbred)
○ Plants with white flowers always produced white flowers
○ Plants with purple flowers always produced purple flowers
● Crossed pure-breeding plants with alternative traits to to produce hybrids which
contained characteristics of one parent
● Mendel dusted female stigma of green pea flower plant with pollen from yellow pea
plants (familial generation) and vice versa
○ The peas were yellow in both cases because yellow is the dominant (first filial F1
generation)
○ Monohybrid Cross: involving hybrid for a single trait
■ Mendel planted the peas to obtain mature F1 plants that he self fertilized
and harvested (fertilized yellow pea plants with other pea plants) and
counted the peas of the resulting F2 generation
● 3:1 ratio of yellow to green peas (Yy x Yy)
○ ¼ breed true for dominant trait
○ ½ will be hybrids
○ ¼ will breed for the recessive trait
○ Pea plants are diploid and there are two alleles of a gene
● For each trait, every plant carries around two copies of a gene
○ Dominant: appeared in all F1 hybrids
■ All genes are not dominant, normally there are variations (not 100%)
■ Incomplete dominance:
■ Codominance:
○ Common misconceptions: Dominant alleles aren’t more prevalent or more “fit”
than recessive alleles and don’t dominate recessive alleles
○ Recessive: remained hidden in F1 hybrids but reappeared in F2 generation
● Each gene comes in alternative forms (alleles)
○ Ex: gene for seed color has yellow and green alleles
● Monohybrids: individuals having two different alleles for a single trait
● During the formation of eggs and sperm, two copies of gene in each parent separate so
each gamete only receives one allele for each trait
● Law of Segregation: two alleles for each trait separate during gamete formation and
unite at random, at fertilization, from each parent
○ Each gamete has ½ chance of carrying dominant allele and ½ chance of carrying
recessive
